The present disclosure relates to dynamoelectric machines and, more particularly, stator core and coil assemblies thereof.
Dynamoelectric machines include alternating current (AC) induction motors having a stator and a rotor. The stator typically includes a stack of laminations formed and arranged in a substantially cylindrical shape having a plurality of longitudinally extending slots. Coils of wire, typically made of copper, are placed within the slots and connected to a source of alternating current. Magnetic fields created by the flow of alternating current through the coils induce magnetic fields in the adjacent rotor, causing the rotor to rotate about the center of the stator.
In one embodiment of such an AC induction motor, the stator is in the form of a cylinder positioned within and surrounded by a rotor in the form of a hollow cylinder. Such a design is useful in machines such as cooling fans, in which fan blades may be attached to and driven by the rotor.
AC induction motors often are utilized in harsh environments. One aspect of such harsh environments is that the alternating current to the stator is developed by an invertor and may include undesirable harmonics and voltage spikes. Such harmonics and voltage spikes cause the current flowing through the coils of the stator assembly to break through the electrical insulation material. This dielectric breakdown caused by voltage spikes and harmonics may create a partial discharge or a corona discharge. A partial discharge frequently begins at voids, cracks or inclusions within a solid dielectric, at conductor-dielectric interfaces within solid or liquid dielectrics, or in bubbles within liquid dielectrics. Partial discharges also may occur along the boundary between different insulating materials. Such partial discharges cause progressive deterioration of insulating materials, which may lead to electrical breakdown, shorting and damage to the stator components.
Accordingly, there is a need for a heavy duty stator core and coil assembly that exhibits superior resistance to partial discharge and corona discharge in response to an AC current having undesirable harmonics and voltage spikes.